Trigonometry is the highest-weight topic in CBSE Class 10 Maths at 12 marks. It covers Trigonometric Ratios/Identities and Applications (Heights and Distances). Both are learnable with the right strategy.
Trigonometric Ratios Table (Must Know From Memory)
| Ratio | 0 deg | 30 deg | 45 deg | 60 deg | 90 deg |
|---|---|---|---|---|---|
| sin | 0 | 1/2 | 1/sqrt2 | sqrt3/2 | 1 |
| cos | 1 | sqrt3/2 | 1/sqrt2 | 1/2 | 0 |
| tan | 0 | 1/sqrt3 | 1 | sqrt3 | undefined |
All Trigonometric Identities for Class 10
- sin2A + cos2A = 1 (and rearrangements)
- 1 + tan2A = sec2A
- 1 + cot2A = cosec2A
- Complementary angle: sin(90-A) = cosA, tan(90-A) = cotA
Identity Proof Questions — The Method
- 1.Start from the more complex side
- 2.Convert everything to sin and cos if stuck
- 3.Use the three Pythagorean identities to simplify
- 4.Factorise using a2-b2 = (a+b)(a-b) when you see difference of squares
Tip
Master these 5 proof types: simple substitution, squaring both sides, adding fractions, factorising, dividing by sin or cos. Practise 2 of each type daily.
Heights and Distances — The 3 Rules
- 1.Always draw the right-angled triangle from the given information first
- 2.Angle of elevation is upward from horizontal; angle of depression is downward
- 3.Use tan(angle) = height/distance for most problems